Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Transparency”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Recent progress in in-situ visualization of electrochemical reactions in electrochemical energy devices

A growing body of evidence indicates that bubble dynamics are crucial performance-limiting factors on electrochemical reactions and energy conversion efficiencies in both half-cell and full cell device levels. This review aims to summarize the recent progress in in-situ visualization characterizations of electrochemical reactions and reactant/product transport in electrochemical energy systems. The latest achievements of various new electrodes, transparent cell designs, and development for simultaneous visualization of reactions at both electrodes and electrolyte/electrode interface are highlighted. The new insights into the influence of bubbles on reaction sites and associated electrochemical performances are discussed. Lastly, some perspectives on potential strategies for mitigating the bubble-induced energy losses are proposed for future research directions and opportunities in water electrolysis and other electrochemical energy systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of helical micro-fins on two-phase flow behavior of R410A evaporating in horizontal round tubes obtained through visualization

This paper presents a new approach in visualization of the evaporation mechanism and the two phase flow. The visualization test section is a transparent micro-fin tube made by 3D printing. The 3D printing technology helps reproduce the real geometry in commercial metal micro-fin tubes. Even though the wall material is different from the real metal, this new method provides a more complete understanding of the mechanisms of flow boiling and the heat transfer enhancement due to micro-fin geometry. To investigate the effect of micro-fin geometries on two-phase flow behavior, R410A flow boiling experiments are conducted at 1°C saturation temperature and visualized through a clear smooth tube and micro-fin tubes of 0°, 10° and 18° helix angles. The results showed that the annular flow pattern in the helical micro-fin tube occurred at a lower vapor quality than the smooth and axial micro-fin tubes. Helix angle affects the transition boundary of stratified wavy flow to wavy annular flow, which shifts downward (to lower mass flux and vapor quality conditions) as the helix angle increases. Other transitions are not significantly affected by the helix angle. Helical micro-fin tubes with different groove directions were made to understand the flow behavior on the upward side and downward side of the tube.

3D printing↗
DOE OSTI2020

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

In this report a novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

14 SOLAR ENERGY↗
DOE OSTI2020

Sputtered indium tin oxide as a recombination layer formed on the tunnel oxide/poly-Si passivating contact enabling the potential of efficient monolithic perovskite/Si tandem solar cells

We focus on utilizing sputtered indium tin oxide (ITO) as a recombination layer, having low junction damage to an n-type silicon solar cell with a front-side tunnel oxide passivating electron contact, thereby enabling the development of a high efficiency monolithic perovskite/Si tandem device. High transparency and low resistivity ITO films are deposited via low power DC magnetron sputtering at room temperature onto a front-side thin SiO x /n + poly-Si contact in a complete Cz n-Si cell with a back-side Al 2 O 3 /SiN x passivating boron-diffused p + -emitter on a random pyramid textured surface. We report the cell characteristics before and after ITO sputtering, and we find a cure at 250 °C in air is highly effective at mitigating any sputtering induced damage. Our ITO coated sample resulted in an implied open-circuit voltage (iV oc ) of 684.7 ± 11.3 mV with the total saturation current density of 49.2 ± 14.8 fA/cm 2 , an implied fill factor (iFF) of 81.9 ± 0.8%, and a contact resistivity in the range of 60 mΩ-cm 2 to 90 mΩ-cm 2 . After formation of a local Ag contact to the rear emitter and sputtered ITO film as the front-side contact without grid fingers, the pseudo-efficiency of 20.2 ± 0.5% was obtained with the V oc of 670.4 ± 7 mV and pseudo FF of 77.3 ± 1.3% under simulated one sun with the calculated short-circuit current density of 30.9 mA/cm 2 from the measured external quantum efficiency. Furthermore, our modelling result shows that efficiency exceeding 25% under one sun is practically achievable in perovskite/Si tandem configuration using the ITO recombination layer connecting a perovskite top cell and a poly-Si bottom cell.

14 SOLAR ENERGY↗
DOE OSTI2022

Heteroatom substitution for the development of near-IR lumiphores

Near-IR (NIR) lumiphores are advantageous for biological applications as their emission falls within the tissue-transparent region. Furthermore, these dyes suffer from low quantum yields as a consequence of their low transition energy. Heteroatom substitution has recently been successfully used to bathochromically shift emission in various dye scaffolds while maintaining bright emission.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Plasmon-Induced Hot-Carrier Excited-State Dynamics in Plasmonic Semiconductor Nanocrystals

The variance of carrier relaxation pathways for WO 3–x plasmonic semiconductor nanocrystals (PSNCs) is monitored by transient absorption spectroscopy following excitation of the localized surface plasmon resonance (LSPR) versus the optical band gap (E g,opt ). Excitation of the LSPR leads to efficient hot carrier population above the Fermi level in WO 3–x via Landau damping, in analogy to noble metal LSPR relaxation mechanisms. Hot carrier depopulation occurs on the femtosecond timescale, observed as the concomitant recovery of an LSPR bleach with the appearance of discrete interband and intraband photoinduced absorption features. Further, by comparison, the direct excitation of E g,opt results in trion recombination at donor–acceptor sites within the WO 3–x NC, consistent with exciton decay dynamics observed for typical wide-band-gap semiconductor NCs. From the analysis of pump power dependency data, a hot-carrier electron–phonon coupling constant of 1.47 × 10 11 J K –1 s –1 cm –3 is extracted. The direct comparison of the decay dynamics following E g,opt versus LSPR excitation confirms that the observed plasmon in trioctylphosphine oxide passivated, spherical WO 3–x is a resonance state in which hot carriers are generated only from excitation on resonance with the LSPR frequency. This study on WO 3–x PSNCs provides a toolset that can be used to evaluate the role of hot carriers following LSPR excitation of n-type, plasmonic transparent conducting oxide NCs, where enhancement of photocatalysis, photovoltaic performance, and optical enhancement has been reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Indium Tin-Doped Oxide Interactions with Solvent Radiolysis Products

Transparent conductive oxides (TCOs), such as indium tin-doped oxide (ITO), are ubiquitous as components of electronics and are ideal electrode substrates for catalysis, energy transformation reactions, and energy storage applications. Recently, researchers have recognized their effectiveness as electrode materials for manipulating actinide oxidation states in solution. Despite their popularity as electrode materials, prior studies focused extensively on the direct radiolysis of TCO materials in air and rarely examined these effects within a solution, limiting our fundamental understanding of the interactions between solvent radiolysis products and these substrates in high radiation environments. Here, in this study, we characterize the effects of solvent radiolysis products—arising from the gamma irradiation of water, aqueous nitric acid solutions, and n-dodecane—on the composition, surface speciation, and band structure of ITO thin films on a glass substrate as a function of absorbed dose using UV-visible spectroscopy, scanning electron microscopy, photoelectrochemistry, and X-ray photoelectron spectroscopy. Our work demonstrates that mesoporous thin film electrodes of ITO exposed to gamma radiation in each solvent accumulate defects and exhibit solvent and dose dependent changes to their surface and interfacial properties. These electrodes maintain their electrochemical function and improve their photoelectrochemical performance up to at least 100 kGy of accumulated gamma dose, confirming their utility in solvents exposed to ionizing radiation fields.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Solvent–Solvent Correlations across Graphene: The Effect of Image Charges

Wetting experiments show pure graphene to be weakly hydrophilic, but its contact angle (CA) also reflects the character of the supporting material. Measurements and Molecular Dynamics simulations on suspended and supported graphene often reveal a CA reduction due to the presence of the supporting substrate. A similar reduction is consistently observed when graphene is wetted from both sides. The effect has been attributed to transparency to molecular interactions across the graphene sheet, however, the possibility of substrate-induced graphene polarization has also been considered. Computer simulations of CA on graphene have so far been determined by ignoring the material’s conducting properties. We improve the graphene model by incorporating its conductivity according to the Constant Applied Potential Molecular Dynamics. Using this method, we compare the wettabilities of suspended graphene and graphene supported by water by measuring the CA of cylindrical water drops on the sheets. The inclusion of graphene conductivity and concomitant polarization effects lead to a lower CA on suspended graphene but the CA reduction is significantly bigger when the sheets are also wetted from the opposite side. The stronger adhesion is accompanied by a profound change in the correlations among water molecules across the sheet. While partial charges on water molecules interacting across an insulator sheet attract charges of the opposite sign, apparent attraction among like charges is manifested across the conducting graphene. The change is associated with graphene polarization, as the image charges inside the conductor attract equally signed partial charges of water molecules on both sides of the sheet. Additionally, by using a non-polar liquid (diiodomethane), we affirm a detectable wetting translucency when liquid-liquid forces are dominated by dispersive interactions. Furthermore, our findings are important for predictive modeling toward a variety of applications including sensors, fuel cell membranes, water filtration, and graphene-based electrode materials in high-performance supercapacitors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

Dynamically tunable membrane metasurfaces for infrared spectroscopy and strong light-matter interactions

Mid-infrared spectroscopy enables biochemical sensing by identifying vibrational molecular fingerprints, but it faces limitations in instrumentation portability and analytical sensitivity. Optical metasurfaces with strong mid-infrared photonic resonances provide an attractive solution towards on-chip spectrometry and sensitive molecular detection, yet their static nature hinders their anticipated impact. Here, we introduce and demonstrate dynamically tunable silicon membrane metasurfaces exhibiting high-Q transmissive resonances in the fingerprint region. By harnessing silicon’s thermo-optical properties, we achieve continuous modulation of coupling-induced transparency (CIT) modes that emerge upon the interference of quasi-bound states in the continuum (q-BICs) and surface lattice modes (SLMs). We measure a spectral tuning rate of 0.06 cm −1 K −1 by continuously sweeping the sharp CIT resonances over a 23.5 cm −1 spectral range across a temperature range of 300–700 K. In the current proof‑of‑concept implementation, the dynamic transmission control enables non-contact chemical analysis of polymer films by detecting characteristic absorption bands of polystyrene (1450 and 1492 cm −1 ) and poly(methyl methacrylate) (1730 cm −1 ) without requiring conventional spectrometers. When analyte molecules fill the metasurface-generated photonic cavities, we demonstrate vibrational strong coupling between the poly(methyl methacrylate)’s carbonyl band and the CIT mode, manifested in a Rabi splitting of ~43 cm −1 . Our results establish a new photonic platform that unites spectral precision, strong field enhancement, and reconfigurability, offering diverse potential for compact mid-infrared spectroscopy, molecular sensing, and programmable polaritonic photonics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Tailoring SnO 2 , (Mg,Zn)O, and Ga:(Mg,Zn)O electro-optical properties and stability for solar cells

The electron density, mobility, bandgap, and band alignment of transparent conducting oxides (TCOs) can be tailored by adjusting composition and stoichiometry, thereby enabling interface engineering for diverse semiconductor applications. For example, solar cell efficiency can change enormously by adjusting TCO properties. At the same time, these TCO properties can shift during the deposition of other layers, anneals, and device operation. An ideal TCO should have tunable but stable electro-optical properties. Here, we deposit SnO 2 , (Mg,Zn)O (MZO), and Ga:(Mg,Zn)O (GMZO) films on glass and measure electro-optical characteristics before and after reducing, inert, oxidizing, and CdCl2 anneals over a range of temperatures. Electron density generally increases in the progression from oxidizing to inert and reducing ambients. SnO 2 is relatively stable compared to MZO but has less flexibility for interface engineering. We investigate GMZO as a similar but more stable alternative to MZO.The addition of Ga to MZO has significant effects on electron density and improves electro-optical stability, which can be advantageous for semiconductor applications. Furthermore, we demonstrate that GMZO can be readily incorporated into solar cells.

14 SOLAR ENERGY↗
DOE OSTI2021

Glass/glass photovoltaic module reliability and degradation: a review

Glass/glass (G/G) photovoltaic (PV) module construction is quickly rising in popularity due to increased demand for bifacial PV modules, with additional applications for thin-film and building-integrated PV technologies. G/G modules are expected to withstand harsh environmental conditions and extend the installed module lifespan to greater than 30 years compared to conventional glass/backsheet (G/B) modules. With the rapid growth of G/G deployment, understanding the outdoor performance, degradation, and reliability of this PV module construction becomes highly valuable. In this review, we present the history of G/G modules that have existed in the field for the past 20 years, their subsequent reliability issues under different climates, and methods for accelerated testing and characterization of both cells and packaging materials. We highlight some general trends of G/G modules, such as greater degradation when using poly(ethylene-co-vinyl acetate) (EVA) encapsulants, causing the industry to move toward polyolefin-based encapsulants. Transparent backsheets have also been introduced as an alternative to the rear glass for decreasing the module weight and aiding the effusion of trapped gaseous degradation products in the laminate. New amendments to IEC 61215 standard protocols for G/G bifacial modules have also been proposed so that the rear side power generation and UV exposure will be standardized. We further summarize a suite of destructive and non-destructive characterization techniques, such as current-voltage scans, module electro-optical imaging, adhesion tests, nanoscale structural/chemical investigation, and forensic analysis, to provide deeper insights into the fundamental properties of the module materials degradation and how it can be monitored in the G/G construction. This will set the groundwork for future research and product development.

14 SOLAR ENERGY↗
DOE OSTI2021

In 2 O 3 -Ga 2 O 3 Alloys as Potential Buffer Layers in CdTe Thin-Film Solar Cells

The efficiency of state-of-the-art Cd Te solar cells remains limited by the relatively low open-circuit voltage (V OC ). Improving the front interface is key towards realizing a higher V OC after achieving the necessary bulk carrier density and lifetime. Recent efforts in identifying buffer layers beyond Cd S have focused on Mg x Zn 1-x O, which offers tunability of the band offsets, but often suffers from high interfacial defect densities. Ga 2 O 3 -based buffer layers demonstrate tremendous improvements in interfacial defect passivation in crystalline silicon and dye-sensitized solar cells, leading to record high V OC , yet remain largely unexplored in Cd Te-based devices. Here, we perform hybrid density-functional-theory calculations to investigate pure Ga 2 O 3 and InGaO 3 alloys as a window layer in Cd Te photovoltaics. We report calculated band offsets for several pairs of solid-solid interfaces comprising transparent conducting oxide (TCO) and Cd Te heterojunctions. The results support a large conduction band offset spike of 0.67 eV for the Cd Te/Ga 2 O 3 (100) interface, while the offset is reduced to 0.18 eV for the InGaO 3 alloy and matches closely with the preferred optimum value of 0.2 eV. Device-level modeling tests of Cd Te solar cells integrating our results indicate that the highest efficiency is achieved with InGaO 3 acting both as a buffer layer and TCO. Finally, our results suggest that alloys of In 2 O 3 and Ga 2 O 3 may be attractive alternatives to Mg x Zn 1-x O for tailoring optimal conduction-band offsets of the buffer and TCO layers in high-efficiency Cd Te thin-film solar cells.

14 SOLAR ENERGY↗
DOE OSTI2022

Nonclassical light from finite-range interactions in a two-dimensional quantum mirror

Excitons in a semiconductor monolayer form a collective resonance that can reflect resonant light with extraordinarily high efficiency. We investigate the nonlinear optical properties of such atomistically thin mirrors and show that finite-range interactions between excitons can lead to the generation of highly nonclassical light. We describe two scenarios, in which optical nonlinearities arise either from direct photon coupling to excitons in excited Rydberg states or from resonant two-photon excitation of Rydberg excitons with finite-range interactions. The latter case yields conditions of electromagnetically induced transparency and thereby provides an efficient mechanism for single-photon switching between high transmission and reflectance of the monolayer, with a tunable dynamical timescale of the emerging photon-photon interactions. Remarkably, it turns out that the resulting high degree of photon correlations remains virtually unaffected by Rydberg-state decoherence, in excess of nonradiative decoherence observed for ground-state excitons in two-dimensional semiconductors. This robustness to imperfections suggests a promising approach to quantum photonics at the level of individual photons.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structure-property relationships and mobility optimization in sputtered La-doped BaSn O 3 films: Toward 100cm 2 V -1 s -1

he wide band gap semiconducting perovskite BaSnO 3 is of high current interest due to outstanding room temperature mobility at high electron density, fueled by potential applications in oxide, transparent, and power electronics. Due in part to a lack of lattice-matched substrates, BaSnO 3 thin films suffer from high defect densities, however, limiting electron mobility. Additionally, the vast majority of BaSnO 3 thin film research has focused on pulsed laser deposition or molecular beam epitaxy. In this work, we present an exhaustive optimization of the mobility of Ba 0.98 La 0.02 SnO 3 films grown by a scalable, high-throughput method: high-pressure-oxygen sputter deposition. Considering target synthesis conditions, substrate selection, buffer layer structure, deposition temperature, deposition rate, thickness, and postdeposition annealing conditions, and by combining high-resolution x-ray diffraction, reciprocal space mapping, rocking curve analysis, scanning transmission electron microscopy, atomic force microscopy, and temperature-dependent electronic transport measurements, detailed understanding of synthesis-structure-property relationships is attained. Optimized room temperature mobility of 96 cm 2 V –1 s –1 is achieved in vacuum-annealed GdScO 3 (110)/BaSnO 3 (120 nm)/Ba 0.98 La 0.02 SnO 3 (200 nm) heterostructures, as well as 92 cm 2 V –1 s –1 on unbuffered substrates and 87 2 V –1 s –1 without postdeposition annealing. These results, including important trends in defect densities and a surprising dependence of mobility on lattice mismatch, substantially expand the understanding of the interplay between deposition conditions, microstructure, and transport in doped BaSnO 3 films, establishing competitive mobilities in films fabricated via a scalable, high-throughput, industry-standard technique.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Color symmetry and confinement as an underlying superconformal structure in holographic QCD

Dedicated to the memory of our colleague, Harald Fritzsch, who, together with Murray Gell-Mann, introduced the color quantum number as the exact symmetry responsible for the strong interaction, thus establishing quantum chromodynamics (QCD) as a fundamental non-Abelian gauge theory. A basic understanding of hadron properties, however, such as confinement and the emergence of a mass scale, from first principles QCD has remained elusive: Hadronic characteristics are not explicit properties of the QCD Lagrangian and perturbative QCD, so successful in the large transverse momentum domain, is not applicable at large distances. In this article, we shall examine how this daunting obstacle is overcome in holographic QCD with the introduction of a superconformal symmetry in anti de Sitter (AdS) space which is responsible for confinement and the introduction of a mass scale within the superconformal group. When mapped to light-front coordinates in physical spacetime, this approach incorporates supersymmetric relations between the Regge trajectories of meson, baryon and tetraquark states which can be visualized in terms of specific SU(3) C color representations of quarks. Finally, we will also briefly discuss here the implications of holographic models for QCD color transparency in view of the present experimental interest.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Conducting more inclusive solar geoengineering research: A feminist science framework

Solar geoengineering, or deliberate climate modification, has been receiving increased attention in recent years. Given the far-reaching consequences of any potential solar geoengineering deployments, it is prudent to identify inherent biases, blind spots, and other potential issues at all stages of the research process. Here we articulate a feminist science-based framework to concretely describe how solar geoengineering researchers can be more inclusive of different perspectives and potentially contradictory conclusions, in the process illuminating potential implicit bias and enhancing the conclusions that can be gained from their studies. Importantly, this framework is an adoptable method of practice that can be refined, with the aim of conducting better research in solar geoengineering. As an illustration, we retrospectively apply this framework to a well-read solar geoengineering study (also led by the first author of this study), improving transparency by revealing its implicit values, conclusions made from its evidence base, and the methodologies that study pursues. We conclude here with a set of recommendations for the geoengineering research community whereby more inclusive research can become a regular part of practice. Throughout this process, we illustrate how feminist science scholars can use this approach to study climate modeling.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Improvement of screen-printable metallization paste for low-cost silicon solar cells utilizing silver coated copper powders

This aims of this project were to develop low-cost screen-printable Ag|Cu metallization, as alternative to Ag paste, for contacting PERC solar cells with transparent emitter for high performance and reliability. The intended goal was to achieve 81% fill factor with a screen-printable Ag|Cu paste alternative. This was attempted through a three strand approach including Ag|Cu formulation by SVMT, production using cavitation technology by ACI and contact formation through the understanding of (i) the liquid phase sintering of the nano/macro particles of Ag|Cu to achieve bulk metal with very low series resistance, (ii) optimization of contact firing to avoid penetration of Cu into the silicon bulk, and finally (iii) proper analysis to quantify the contributions of each resistance component and keep the total series resistance at 0.2 Ω-cm2, which would result in high fill factor of 81% by UNC Charlotte. The objectives also involved i) the implementation of glass frit with Cu metal that will etch through the ARC for low contact resistance and adhesion, ii) development of Ag|Cu pastes with the optimized glass frit, iii) investigation of the impact of Cu particle size, morphology and loading on the gridline resistance, iv) narrow gridline screen designs along with narrow gridline prints, v) development of fast belt speeds of up to 375 inches per minute (ipm) sintering, and vi) stability study on Ag|Cu contact to high performance and reliability.

14 SOLAR ENERGY↗